This invention pertains generally to the field of fabrication of electronic devices. More particularly, this invention relates to mechanical scribing methods of forming a patterned metal layer which is useful in an electronic device. More specifically, this invention pertains to new methods of forming a patterned metal layer in an electronic device, wherein the metal layer is in contact with an underlying organic polymeric layer (e.g., a conductive or semiconductive organic polymeric layer), which methods comprise mechanically scribing the metal layer with a mechanical scribing instrument to form the patterned metal layer.
Throughout this application, various publications, patents, and published patent applications are referred to by an identifying citation; full citations for these documents may be found at the end of the specification immediately preceding the claims. The disclosures of the publications, patents, and published patent specifications referenced in this application are hereby incorporated by reference into the present disclosure to more fully describe the state of the art to which this invention pertains.
With the advent of solid state electronics and the integrated circuit (IC) chip industry, many new methods for the fabrication and processing of solid state electronic devices have been developed. For example, many solid state electronic devices are manufactured by depositing and processing, often sequentially, one or more relatively thin layers of specific materials (e.g., metals, alloys, semiconductors) on a substrate, in order to form a three-dimensional device with the desired electronic function. In many cases, one or more of these layers are xe2x80x9cpatterned,xe2x80x9d that is, fabricated or processed to possess a pre-determined shape within the two-dimensional plane of the layer, to provide additional structure to the device.
Many methods for fabricating patterned layers of specific materials have been developed. One common class of patterning methods may be conveniently classified as photolithography methods. In such methods, selected areas of a surface are protected or xe2x80x9cmaskedxe2x80x9d (for example, by a shadow mask pressed against the layer, or by a layer of photoresist processed with the aid of a shadow mask), while the unmasked areas are exposed to processes such as the introduction of impurities, deposition of thin films, removal of material by etching, and the like.
For example, it is often possible to form a patterned metal layer by first pressing a xe2x80x9cnegativexe2x80x9d shadow mask against the surface, and subsequently vapor depositing the metal. The metal is deposited only on the open areas within the shadow mask (hence creating a xe2x80x9cpositivexe2x80x9d image) and not on those areas protected by the shadow mask. Following deposition, the shadow mask is withdrawn, yielding the patterned metal layer. In another method, a continuous metal layer is first deposited, and then coated with uncured photoresist (e.g., a polymeric material which is cured, and thus rendered insoluble in certain solvents, by exposure to an appropriate wavelength of light). A xe2x80x9cnegativexe2x80x9d shadow mask is pressed against the photoresist layer, and the assembly exposed to the appropriate light (e.g., ultraviolet light), thereby curing the photoresist in the open areas within the shadow mask. The shadow mask is withdrawn and the uncured photoresist removed, often using wet chemical methods (e.g., by washing with an appropriate solvent), to expose areas of metal. The exposed metal is then removed, for example, using wet chemical etching methods, and finally the cured photoresist is removed to yield the desired patterned metal layer (with a xe2x80x9cpositivexe2x80x9d image pattern).
Screen printing methods have also been employed in the fabrication of patterned metal layers, typically with the aid of an (often electrically conducting) ink or paste which comprises metal particles. Screen printing methods, which may conveniently be considered refined stenciling methods, typically employ a stencil (akin to the photolithography mask) in combination with a screen (a woven fabric, generally of polyester, nylon, or stainless steel). During printing, a squeegee presses the ink or paste through the screen; where the stencil permits, the ink or paste is applied to the surface to be patterned. The stencil and screen are then removed to yield the printed pattern. Following screen printing with metallic inks and pastes, the layer is often heated, dried, and/or cured.
Recently, laser methods, such as laser scribing, laser ablation, and laser etching, have been used in the fabrication of patterned layers. Typically, in these methods, an intense focused laser beam is rastered across the surface, causing the illuminated material to be vaporized, sputtered, or otherwise removed, leaving a groove, trench, via, trough, or other indentation with a shape determined by the path of the laser beam, and a depth determined by the intensity and raster speed of the laser beam.
Many of these methods are particularly well adapted for the specific materials. For example, for metals which can be easily vapor deposited, photolithography methods employing a negative shadow mask are often very useful. For more refractory materials, such as oxides, nitrides, and many inorganic semiconductor materials, laser ablation methods may be better suited. Whichever method is employed, an important factor for assessing that method""s usefulness is the quality of the resulting pattern, determined, for example, by the sharpness of the edges of the pattern and the amount and size of any residual debris.
Many electronic devices comprise a metal layer, often in the form of a relatively thin layer of metal material. Such metal layers, which often function as an electrode for the electronic device, are often patterned. For example, many common electronic devices require a thin patterned layer of conducting metal over an insulating or semiconducting substrate, with a pattern comprising a large number of very narrow electrically isolated bars (e.g., stripes) of metal, each separated by a very narrow gap. In such cases, a particularly useful patterning method would be one which offers both very sharp pattern edges (facilitating narrow metal bars, narrow gaps, and thus a large number of bars per unit distance perpendicular to the bar (i.e., high resolution) with a large xe2x80x9cfill factorxe2x80x9d (i.e., ratio of active to non-active area)) and residual debris which is small compared to the dimensions of the gap (so that the debris is unlikely to bridge the gap and cause an inadvertent electrical short).
The present invention pertains to new methods of forming a patterned metal layer (which comprise mechanically scribing the metal layer with a mechanical scribing instrument to form the patterned metal layer) and which address many or all of these requirements.
Mechanical scribing methods are well known to those of skill in the art. However, the primary use of mechanical scribing in the manufacture of electronic devices has been to effect separation (e.g., of dice from a larger wafer). Typically, a wafer is first mechanically scribed or scored and subsequently fractured or cleaved along the scribe or score line. Such methods are widely used to effect the separation of partially or completely finished individual electronic devices (e.g., dice) from a larger wafer. For example, large numbers of electronic devices are often fabricated simultaneously on a single wafer; when the fabrication is partially or fully complete, the wafer is scribed or scored (often using mechanical scribing methods), and individual devices are cleaved off.
Methods of separating individual dice from a larger wafer which employ, as a first, step, mechanical scribing to form a scribe line for cleaving have apparently been disclosed (see, for example, Nath et al., 1992, at column 13, where a scribe line through a metallic top layer and partially through an underlying semiconductor layer is described). Methods of cleaving semiconductor diode lasers from a larger wafer which employ a diamond circular saw blade to cut a groove through layers of metal and into a gallium arsenide substrate have apparently been disclosed (see, for example, Woolhouse et al., 1980, at column 4). Methods of dividing metal plated semiconductor wafers, which include the step of mechanically scribing through a metal layer and a photoresist layer and partially into the underlying semiconductor, have apparently been disclosed (see, for example, Fair et al., 1977).
Mechanical scribing methods have also apparently been employed in the formation of patterned layers of certain classes of materials, for example, oxides, such as indium tin oxide (ITO), and semiconductor substrates. Methods of making photoresponsive arrays have been disclosed which apparently may employ mechanical scribing methods to pattern inorganic semiconductor layers (see, for example, Ondris, 1988 and Ondris, 1989, both at column 10). Methods of making thin film solar cells which apparently employ mechanical scribing methods to pattern layers of copper indium diselenide and zinc oxide have also been disclosed (see, for example, Gay, 1987, at column 12). Methods of patterning indium tin oxide (ITO) layers, including mechanical scribing methods, have apparently been disclosed (see, for example, Stocker et al., 1994, at column 5). Methods of patterning optically transparent electrically conductive layers, such as ITO, indium oxide, zinc oxide, and tin oxide, on transparent substrates for use in photovoltaic devices, including mechanical scribing methods, have apparently been disclosed (see, for example, Basol et al., 1987, at column 5). Methods of fabricating solar cells, which apparently include patterning a back metal electrode using screen printing or mechanical scribing methods have apparently been disclosed (see, for example, Morel et al., 1985, at column 7). Methods of fabricating liquid crystal display devices, which include a method of patterning a transparent electrically conductive layer on a substrate have apparently been disclosed (see, for example, Crossland et al., 1983). Methods of fabricating solar cells, which include a method of patterning a tellurium layer on a cadmium telluride substrate which may employ mechanical scribing, have apparently been disclosed (see, for example, Milnes, 1984).
Although mechanical scribing methods have been used in the manufacture of electronic devices, as described above, mechanical scribing methods have never been employed in the patterning of a metal layer in contact with an underlying organic polymeric layer (e.g., a conductive or semiconductive organic polymeric layer). The disinterest in mechanical scribing as a method for patterning metal layers may be attributed to poor results previously obtained (e.g., rough pattern edges, large fragments of debris) and to the availability of other apparently successful, albeit relatively complex and expensive, methods (e.g., photolithography).
The inventor has discovered the surprising and unexpected result that a metal layer in contact sequence with an underlying organic polymeric layer, may be successfully and usefully patterned using mechanical scribing methods. By comparison, when an organic polymeric layer, without a metallic overlayer, is mechanically scribed, extremely poor results are obtained: the scribe line has very poorly defined and irregular edges, and copious amounts of large debris particles. In contrast, when an organic polymeric layer/metallic overlayer structure is mechanically scribed, desirable results are obtained: the scribe line has well defined and regular edges, and dimensionally small debris as compared with the dimensions of the scribe line. Without wishing to be bound by any particular theory, the inventor postulates that the metal overlayer provides a protecting layer in which the scribe cut is cleanly initiated, and that underlying polymer layer may act as a sort of xe2x80x9ccutting mat,xe2x80x9d thereby facilitating the sharp and clean scribing of the metal overlayer.
Thus, the present invention pertains to new methods of forming a patterned metal layer in an electronic device, wherein the metal layer is in contact with an underlying organic polymeric layer (e.g., a conductive or serniconductive organic polymeric layer), which methods comprise mechanically scribe layer with a mechanical scribing instrument to from the patterned metal layer. In comparison with commonly employed patterning methods (e.g., photolithography, laser ablation), the mechanical scribing methods of the present invention are procedurally simpler, faster and often cheaper.
One aspect of the present invention pertans to methods of forming a patterned metal layer in an electronic device, wherein the metal layer is in contact with an underlying organic polymeric layer (e.g., a conductive or semiconductive organic polymeric layer), which methods comprise mechanically scribing the metal layer with a mechanical scribing instrument to form the patterned metal layer.
In one embodiments the present invention pertains to a method of forming a patterned metal layer in an electronic device, which device comprises, in contact sequence, a support layer, an organic polymeric layer, and said metal layer, said method comprising the step of mechanically scribing said metal layer with a mechanical scribing instrument to form said patterned metal layer; wherein said mechanical scribing instrument scribes through the entire thickness of said metal layer; wherein said mechanical scribing instrument scribes through none, some, or all of the thickness of said organic polymeric layer; wherein said mechanical scribing instrument scribes through none or some, but not all, of the thickness of said support layer.
In one embodiment, the present invention pertains to a method of forming a patterned metal electrode layer in an electronic device, which device comprises, in contact sequence, a substrate layer, a first electrode layer, an organic polymeric layer, and said metal electrode layer, said method comprising the step of mechanically scribing said metal electrode layer with a mechanical scribing instrument to form said patterned metal electrode layer; wherein said mechanical scribing instrument scribes through the entire thickness of said metal electrode layer; wherein said mechanical scribing instrument scribes through none, some, or all of the thickness of said organic polymeric layer; wherein said mechanical scribing instrument scribes through none or some, but not all, of the thickness of said first electrode layer; and, wherein said mechanical scribing instrument scribes through none or some, but not all, of the thickness of said substrate layer.
In one embodiment, the present invention pertains to a method of forming a patterned metal cathode layer in an electronic device, which device comprises, in contact sequence, a substrate layer, an anode layer, an organic polymeric layer, and said metal cathode layer, said method comprising the step of mechanically scribing said metal cathode layer with a mechanical scribing instrument to form said patterned metal cathode layer; wherein said mechanical scribing instrument scribes through the entire thickness of said metal cathode layer; wherein said mechanical scribing instrument scribes through none, some, or all of the thickness of said organic polymeric layer; wherein said mechanical scribing instrument scribes through none or some, but not all, of the thickness of said anode layer; and, wherein said mechanical scribing instrument scribes through none or some, but not all, of the thickness of said substrate layer.
In one embodiment, the present invention pertains to a method of forming a patterned electron-injecting metal cathode layer in a light emitting diode, which light emitting diode comprises, in contact sequence, a transparent substrate layer, a transparent hole-injecting anode layer, an emissive organic polymeric layer comprising an electroluminescent polymer, and said metal cathode layer, said method comprising the step of mechanically scribing said metal cathode layer with a mechanical scribing instrument to form said patterned metal cathode layer; wherein said mechanical scribing instrument scribes through the entire thickness of said metal cathode layer; wherein said mechanical scribing instrument scribes through none, some, or all of the thickness of said emissive organic polymeric layer; wherein said mechanical scribing instrument scribes through none or some, but not all, of the thickness of said anode layer; and, wherein said mechanical scribing instrument scribes through none or some, but not all, of the thickness of said substrate layer.
In one embodiment, the mechanical scribing instrument is metallic. In one embodiment, the mechanical scribing instrument is stainless steel. In one embodiment, the mechanical scribing instrument is a stainless steel stylus, a diamond stylus, or a soda lime glass stylus.
In one embodiment, the patterned metal layer comprises one or more bars, stripes, lines, rows, or columns. In one embodiment, the patterned metal layer comprises two or more bars, stripes, lines, rows, or columns. In one embodiment, the patterned metal layer comprises three or more bars, stripes, lines, rows, or columns. In one embodiment, the patterned metal layer comprises ten or more bars, stripes, lines, rows, or columns. In one embodiment, the patterned metal layer comprises one hundred or more bars, stripes, lines, rows, or columns.
In one embodiment, the mechanical scribing instrument passes through at least about 50% of said organic polymeric layer.
In one embodiment, the organic polymeric layer comprises a conductive or semiconductive polymer. In one embodiment, the organic polymeric layer comprises a polymer which is conjugated or which comprises segments of conjugated moieties. In one embodiment, the organic polymeric layer comprises a polymer selected from the group consisting of: polyanilines, polythiophenes, polyquinolines, polyarylenes, polyphenylenes, polyarylenevinylenes, polyphenylenevinylenes, polyacetylenes, polyfurans, and polypyrroles. In one embodiment, the organic polymeric layer comprises a polyphenylenevinylene polymer.
In one embodiment, the electroluminescent polymer is selected from the group consisting of: poly(p-phenylene vinylene)s, poly(arylene vinylene)s, poly(p-phenylene)s, poly(arylene)s, and polyquinolines. In one embodiment, the electroluminescent polymer is a polyphenylenevinylene polymer.
In one embodiment, the organic polymeric layer has a thickness of about 200 xc3x85 to about 2 xcexcm.
In one embodiment, the metal layer comprises one or more metals selected from the group consisting of: lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, strontium, barium, chromium, nickel, platinum, copper, silver, gold, aluminum, tin, lanthanide metals, actinide metals. In one embodiment, the metal layer comprises one or more metals selected from the group consisting of: aluminum, copper, chromium, and gold. In one embodiment, the metal layer comprises a first metal selected from the group consisting of: calcium, barium, and ytterbium; and a second metal selected from the group consisting of: aluminum, copper, chromium, and gold.
In one embodiment, the metal layer has a thickness of about 100 xc3x85 to about 5 xcexcm.
In one embodiment, the first electrode layer or the anode layer comprises one or more materials selected from the group consisting of: metal, metal oxide, graphite, doped inorganic semiconductor, and doped conjugated polymer. In one embodiment, the first electrode layer or the anode layer comprises one or more materials selected from the group consisting of: aluminum, silver, platinum, gold, palladium, tungsten, indium, copper, iron, nickel, zinc, lead, tin oxide, indium/tin oxide, graphite, doped silicon, doped germanium, doped gallium arsenide, doped polyaniline, doped polypyrrole, and doped polythiophene.
In one embodiment, the substrate comprises glass. In one embodiment, the substrate comprises soda lime glass.
Another aspect of the present invention pertains to an electronic device comprising a patterned metal layer which is in contact with an underlying organic polymeric layer (e.g., a conductive or semiconductive organic polymeric layer), and which patterned metal layer was formed by a method of the present invention.
As will be appreciated by one of skill in the art, features of one aspect or embodiment of the invention are also applicable to other aspects or embodiments of the invention.